1. Field of the Invention
The present invention generally relates to mobile communication systems, and more particularly to a system and method for obtaining radiation gain characteristics of a built-in antenna in a mobile communication terminal.
2. Background of the Related Art
A mobile communication terminal (referred to as ‘terminal’, hereinafter) may generally be regarded as any portable device that transmits and receives voice, character, and/or image information with other terminals or devices.
Lately, mobile terminals are being provided with a wireless data service having a reinforced multimedia function. Also, recent trends require that mobile terminals become more compact and light-weight for carrying convenience. To meet these requirements, terminals are now using internal instead of external antennas. Internal antennas can be used to support Bluetooth, wireless LAN, GSM, CDMA and other communication protocols and formats.
FIG. 1 is a cross-sectional view of a mobile terminal 10 having an internal antenna in accordance with the related art, and FIG. 2 is a perspective view of this built-in antenna. As shown in FIG. 1, the terminal includes a main body 3 accommodating a main PCB (Printed Circuit Board) for transmitting and receiving voice and image information in a case 1. The terminal also includes a folder part 5 foldably hinged at one end of the main body and a built-in antenna 6 with one end connected to the main PCB for transmitting and receiving an electric signal to and from the main PCB. Reference numeral 4 denotes a folder case.
As shown in FIG. 2, the built-in antenna includes a carrier 11 fixed at an inner side of the case 1 and spaced apart from the main PCB, a radiator 12 attached at one side of the carrier for radiating electromagnetic waves, and a feeding terminal 14 for electrically connecting the radiator and an antenna terminal 2a of the main PCB through a connection line 13.
In operation, if a user inputs voice information using a microphone in a call standby state, a voice signal is converted into an electric signal, transferred through antenna terminal 2a of the main PCB, feeding terminal 14 and connection line 13, and then finally radiated through radiator 12. The radio signal received through the radiator 12 is transferred to main PCB 2 through connection line 13, feeding terminal 14, and antenna terminal 2a. 
Radio frequency and electromagnetic interference (EMI) are critical factors in the design of mobile terminals and other communication products. EMI signals in particular have a strong potential to affect the operation of the internal components of the terminal, including its electronic device packages. Consequently, the frequency and level of EMI signals radiated outwardly from the interior of an electronic product are often limited.
In effort to solve such problems, electronic products include a shield device for interrupting EMI radiated from each element, or internal elements are packaged in a grounded enclosure.
In FIG. 1, portion A shows an electromagnetic wave shielding film 22 with a certain thickness formed at an inner surface of body part 21, and FIG. 3 is an enlarged sectional view of portion A. Shielding film 22 is made of sequentially plated copper and nickel and operates to shield electromagnetic waves generated from components (e.g., antenna terminal 2a) attached at the main PCB from being outwardly discharged.
In order to maintain the wireless characteristics of the built-in antenna against EMI, a radiator or meander line and microstrip line are simply isolated a certain distance from the main PCB, or the size of the antenna is increased. However, because built-in antenna 6 and main PCB 2 are installed to be isolated from one another by a certain distance, installation space of the built-in antenna must be secured inside the case. This inevitably increases the size of the main body case, which diminishes the ability to make the terminal compact in size.